Fixed rail transportation systems, that include one or more rail vehicles traveling over spaced apart rails of a railway track, have been an efficient way of moving cargo and people from one geographical location to another. In densely populated countries and countries having unimproved road transportation systems, rail vehicles may be the primary means for moving people and cargo. Additionally, rail transportation is used in areas where little to no population exists. Accordingly, there are probably millions of miles of railroad track throughout the world that need to be maintained.
There are over two hundred thousand wayside signaling devices deployed in association with railroad systems throughout the United States. Railroad systems include wayside equipment located along the track, such as switches, signals, and vehicle detectors. Wayside equipment may be defined as, for instance, a track-switch position device, a track occupancy detector, a wayside signaling device, a hot box detector, a hot wheel detector, a dragging equipment detector, a high water detector, a high/wide load detector, an automatic equipment identification system, a highway crossing system, an interlocking controller system, or any other equipment located adjacent the track and used to monitor the status of the track, environmental conditions, and/or railway vehicles. Various wayside equipment devices are located throughout the railroad system, and are thus geographically dispersed and often located at places that are difficult to access.
Railways generally employ wayside signals using color and position of these signals to convey movement authority information to the train crew. These signals are controlled locally by wayside signaling devices. Wayside signaling devices convey information between signal locations using the two rails of the railroad track as electrical conductors to form track circuits. Insulated rail joints are added at signal locations to allow separate track circuits to be formed between two signal locations. Currently, solid-state coded track circuits are used for railroad signaling. Such circuits are usually Direct Current (DC)-coded pulses that are used to convey information between signal locations. These wayside signaling devices rely on insulated rail joints at the wayside signal locations to prevent signals from promulgating to devices not intended to receive the signals.
FIG. 1 depicts a prior art exemplary embodiment of a solid state coded DC track system using insulated joint tracks. A railway track 9 has insulated joints 10 between where adjacent track rails 13 meet. The insulated joints 10 are used to form a block 11, 12 for railroad signaling. Signaling devices 14, 15 at first end of the block, 11, 12 transmits DC coded pulses that are detected and decoded by signaling devices 17, 18 at a second end of the block 11, 12. Depending on signaling devices, signaling, detection, and decoding signal transmission occurs in both directions of the block 11, 12, or in other words also from the second end to the first end. To insure that an intended signal is received, communication between signaling equipment 14, 17, 15, 18 is synchronized within a fixed code frame period. Therefore, the first signaling device 14, 15 within the respective box 11, 12 transmits during a first half of a period and the second signaling device 17, 18 transmits within a second half of the period. The insulated joints 10, retains the signal within a respective block and thus prevents the signal from emitting into another block 11, 12.
While most track components are viewed as being primarily mechanical in nature, many of them also serve an electrical purpose. Rails, ties, ballast, insulated joints, gauge plates, gauge rods and crossing panels in track locations where signals are transmitted through the rail must all have the correct electrical characteristics, as well as the right mechanical properties, in order for the signal equipment to function properly. This includes wayside signaling, cab signaling and crossing warning systems.
In the maintenance of railroad track, insulated joints can be a particular concern. As a mechanical discontinuity in the rails, the insulated joints must often endure a more severe “pounding” than the rails themselves are subjected to. Ballast and sub-grade materials can be affected, and significant “pumping” of the track may occur under heavy rail traffic. Despite all this, insulated joints must maintain a sound mechanical connection, and, ideally, maintain perfect electrical isolation.
In operation, the degree of electrical insulation provided by insulated joints may not be perfect, even when the insulated joints are. This is primarily due to ballast resistance providing an electrically-conductive path around each insulated joint. But every insulated joint's insulation eventually degrades. Thus, railroad owners and users would benefit from a railway where railway maintenance issues directly attributable to insulated railroad joints are reduced.